U.S. patent number 5,622,380 [Application Number 08/531,945] was granted by the patent office on 1997-04-22 for variable nonazide gas generator having multiple propellant chambers.
This patent grant is currently assigned to Automotive Systems Laboratory, Inc.. Invention is credited to Paresh S. Khandhadia, Rickey L. Stratton.
United States Patent |
5,622,380 |
Khandhadia , et al. |
April 22, 1997 |
Variable nonazide gas generator having multiple propellant
chambers
Abstract
A gas generator (10) utilizes at least three segregated
propellant container/combustion chambers (22, 32 and 34), each
having a plurality of nonazide propellant grains (20, 36 and 38)
therein, and an igniter (16) for igniting only the propellant
grains (20) located within the first combustion chamber (22). The
nonazide propellant produces enough heat energy to subsequently
ignite the segregated propellant grains (36 and 38) by forced
convection and/or heat conduction. The output inflation profile can
be tailored to optimally cover a range of 10 to 90 percentile
vehicle occupants.
Inventors: |
Khandhadia; Paresh S. (Troy,
MI), Stratton; Rickey L. (Pontiac, MI) |
Assignee: |
Automotive Systems Laboratory,
Inc. (Farmington Hills, MI)
|
Family
ID: |
24119726 |
Appl.
No.: |
08/531,945 |
Filed: |
September 21, 1995 |
Current U.S.
Class: |
280/736; 102/531;
280/741 |
Current CPC
Class: |
B60R
21/2644 (20130101); B60R 2021/2648 (20130101) |
Current International
Class: |
B60R
21/26 (20060101); B60R 021/26 () |
Field of
Search: |
;280/736,741,740,742,728.1 ;102/530,531,443 ;422/164,165,166 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
4005768 |
|
Aug 1991 |
|
DE |
|
4-345556 |
|
Dec 1992 |
|
JP |
|
5-319199 |
|
Dec 1993 |
|
JP |
|
Primary Examiner: Johnson; Brian L.
Assistant Examiner: English; Peter C.
Attorney, Agent or Firm: Lyon, P.C.; Lyman R.
Claims
We claim:
1. A gas generator having a variable output gas generation rate
comprising:
a housing having a plurality of apertures spaced therein;
a first propellant chamber located within said housing and arranged
to be in fluid communication with said plurality of apertures;
at least a second propellant chamber and third propellant chamber
located within said housing and arranged to be in fluid
communication with said plurality of apertures, wherein said first
and said at least second and third propellant chambers are
respectively separated by a solid barrier element which prohibits
direct fluid communication between the propellant chambers;
a first nonazide propellant charge positioned within said first
chamber having a predetermined burn temperature;
at least a second nonazide propellant charge and third nonazide
propellant charge respectively positioned within said second and
third chambers; and
an igniter positioned within said housing for supplying a flame
front to only said first propellant chamber, wherein the ignition
of said first charge by said flame front produces heat energy which
subsequently conductively ignites said at least second and third
nonazide propellant charges.
2. The gas generator of claim 1 wherein said first, second and
third chambers are radially arranged about said igniter so as to
form a pie configuration.
3. The gas generator of claim 1 wherein said first, second and
third chambers are axially arranged relative to said igniter so as
to form a stacked configuration.
4. The gas generator of claim 1 wherein each of said solid barrier
elements are positioned relative to said housing so as to vary the
size of said first and said at least second and third propellant
chambers to create a desired inflation profile at ignition.
Description
BACKGROUND OF THE INVENTION
The present invention generally relates to gas generators such as
used to inflate air bags in an automobile occupant protection
system, and more particularly to an improved gas generator having a
variable inflation rate output capable of safely achieving a low
onset inflation.
The prior art generally discloses inflation systems for deploying
an air bag in a motor vehicle which provide a single gas generator
in fluid communication with the uninflated air bag. The gas
generator is typically triggered by an air bag firing circuit when
the sensed vehicle acceleration exceeds a predetermined threshold
value, as through the use of an acceleration-responsive inertial
switch and an explosive "squib."
Conventional single gas generator inflation systems suffer from the
disadvantage that the onset pressurization/inflation rate is
generally set to provide an aggressive or rapid initial inflation
in order to achieve a particular inflation time even for an
occupant positioned relatively close to the air bag. However, an
aggressive and uncontrolled onset rate of pressurization becomes
problematic in situations where the occupant is out of position.
More specifically, the rapid pressurization can cause the air bag
to impact against the occupant with enough force to injure the
occupant.
In commonly owned U.S. Pat. No. 5,400,487, Gioutsos et al teach an
inflation system which overcomes the above-described problems by
utilizing a plurality of gas generators which are controllably
ignited to provide a variable inflation profile which can be
tailored to any given occupant position and for any crash type.
While this arrangement dramatically improves the inflation
efficiency so as to maximize an air bag's ability to protect an
occupant, it does so at significantly higher expense and
complexity. More specifically, the multiple gas generators and
squibs add considerable cost to the system, while the firing
control circuitry requires sophisticated processors capable of
accurately timing the various ignition times.
In U.S. Pat. No. 5,009,855, Nilsson discloses a gas generator which
positions an insert within the propellant combustion chamber so as
to partially separate the combustion chamber into two sections
having different volumes. In operation, an igniter generates a
flame front which initially ignites a small portion of the
propellant as the flame front passes through the first section of
the combustion chamber, and then ultimately the remaining
propellant as the flame front passes around the insert and reaches
the second section of the combustion chamber. Nilsson teaches that
the gas volume produced by the first propellant section gently
presses an out-of-position occupant into the vehicle seat before
the second propellant section rapidly inflates the bag to the
maximum volume within the shortest possible time.
While Nilsson discloses a gas generator arrangement which produces
a lower onset rate of inflation, the precise rate of onset can only
be controlled to a small degree since the same igniter flame front
must be used to ignite both propellant sections.
In commonly owned copending U.S. patent application Ser. No.
08/498,852 to DeSautelle et al, filed on Jul. 6, 1995, entitled
"Dual Chamber Nonazide Gas Generator," a gas generator arrangement
is taught which utilizes two isolated propellant chambers to
produce a low onset rate without sacrificing peak inflation
pressure or inflation time. The inherently high ignition
temperatures of a nonazide propellant charge located in the first
chamber produces enough heat energy to conductively ignite the
nonazide propellant charge located in the second chamber.
While the dual chamber nonazide gas generator of U.S. Ser. No.
08/498,852 provides a dramatic improvement in performance over
known gas generators, a need still exists for providing a variable
gas generator which can produce an even greater range of inflation
profiles tailored to more specific firing situations such as 10
percentile and/or out of position vehicle occupants. Therefore, a
need still exists for a gas generator which can satisfactorily
produce variable inflation pressurization with a low onset
rate.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
improved gas generator for use in a vehicle air bag inflation
system which can optimally produce a low onset rate of
pressurization without sacrificing peak inflation pressure or
inflation time.
Another object of the present invention is to provide an improved
gas generator which produces a variable output inflation profile
sufficient to inflate a vehicle air bag to provide optimal
protection for a range of 10 to 90 percentile vehicle
occupants.
Another object of the present invention is to provide an improved
gas generator which utilizes combustion of a first nonazide
propellant charge to conductively ignite a segregated second and
third nonazide propellant charge.
In accordance with the present invention, a gas generator having a
variable output gas generation rate comprises a housing having a
plurality of apertures spaced therein, a first propellant chamber
located within the housing and arranged to be in fluid
communication with the plurality of apertures, and at least a
second and third propellant chamber located within the housing and
arranged to be in fluid communication with the plurality of
apertures. A first nonazide propellant charge is positioned within
the first chamber having a predetermined burn temperature, and
respective second and third nonazide propellant charges are
positioned within the second and third chambers. An igniter is
positioned within the housing for supplying a flame front to only
the first propellant chamber, wherein the ignition of the first
charge by the flame front produces heat energy which subsequently
conductively ignites the second and third nonazide propellant
charges. Isolation of the first, second and third propellant
chambers is achieved by a barrier affixed within the housing. The
barrier effectively impedes the igniter flame front from passing
from the first chamber to the second and/or third chamber. The
chambers can be either radially positioned relative to the igniter
to form a pie configuration, or axially positioned relative to the
igniter to form a stacked configuration.
The present invention will be more fully understood upon reading
the following detailed description of the preferred embodiment in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an upper cross-sectional view of a variable inflator
having three pie configured propellant chambers in accordance with
a first exemplary embodiment; and
FIG. 2 is a cross-sectional view of a second exemplary stacked
configuration inflator embodiment in accordance with the present
invention .
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
As seen in FIG. 1, a variable gas generator or inflator 10 for an
automobile air bag, in accordance with a first exemplary "pie
configured" constructed embodiment of the present invention,
comprises a housing 12, for example, an aluminum forging provided
with a plurality of bag inflating gas discharge orifices (not
shown). The housing 12 has an integral central support tube 14 for
the mounting of a conventional igniter 16 (shown by dashed line).
The igniter 16 is provided with a pair of electrical conductors
(not shown) to facilitate electric ignition of an explosive charge
contained therein.
The igniter tube 14 is provided with at least one aperture 18
disposed at a point underlying the igniter 16. The aperture 18
allows a flame front generated by the igniter 16 to pass to a
nonazide propellant 20 located within a first combustion chamber
22. Three separate barrier walls 24, 26 and 28 are positioned to
extend between the igniter tube 14 and an outer propellant retainer
sleeve 30 to form a second combustion chamber 32 and a third
combustion chamber 34. A nonazide propellant 36 is located within
the second combustion chamber 32, and a nonazide propellant charge
38 is located within the third chamber 34. The retainer sleeve 30
has a plurality of apertures 40 therein to permit a radially
outward passage of gas generated by the propellant 20, 36 and 38. A
filter 42 surrounds the retainer sleeve 30 and comprises a fine
wire mesh annulus that is resiliently axially compressed within the
housing 12 upon assembly thereof. The filter 42 is radially
retained by a relatively heavy wire screen 44 that accommodates
radial expansion of the filter element 42 due to longitudinal
compression upon assembly of the housing components.
In operation, the gases generated by the propellant charges 20, 36
and 38 exit from the respective combustion chambers through the
apertures 40, pass through the filter 42 and the wire mesh screen
44 to exit through the bag inflating orifices located in the
housing 12.
In accordance with the present invention, low, variable, onset
pressurization is achieved by sectioning the combustion area into
the three separate propellant chambers 22, 32 and 34. The barriers
24, 26 and 28 provide a mechanism for preventing the passage of the
flame front generated by the igniter 16 from directly causing
combustion of the propellant charges 36 and 38, respectively
located within chambers 32 and 34. Instead, the heat generated by
the combustion of the first propellant charge 20 causes subsequent
delayed ignition of the propellant charges 36 and 38 by forced
convection and/or conduction. More specifically, the heat energy
inherently flows from the higher temperature chamber 22 to the
cooler chambers 32 and 34, such as by way of apertures 40. Because
the propellant charge located in the first chamber 22 is composed
of a nonazide formula, the amount of heat inherently generated at
combustion is sufficiently high enough to conductively ignite the
propellant charges located within chambers 32 and 34. A
conventional azide propellant mixture would not produce enough heat
energy to ignite a combustion chamber which is completely isolated
from the igniter 16 flame front.
As seen in FIG. 2 of the drawing, a variable output inflator 100 in
accordance with second exemplary "stacked" constructed embodiment
of the present invention comprises four major components, namely, a
housing 102, nonazide propellant charges 104, 106 and 108, a filter
109, and an igniter 110.
Like inflator 10, the inflator housing 102 is formed by two
dish-shaped sections 112 and 114 that are welded together in
inverted nested relationship. The lower housing portion 114
contains a plurality of apertures 116 for the discharge of gas
produced by the propellant into an air bag (not shown).
The housing 102 is provided with a centrally disposed igniter
support tube 118 having a flared lower end portion that is welded
to a complementary boss in the lower housing portion 114. Tube 118
supports the igniter 110 internally thereof, and is welded to the
upper housing portion 112.
The igniter tube 118 is provided with a plurality of apertures 120
disposed in a circumferential array at a point underlying the
igniter 110. The apertures 120 allow a flame front generated by the
igniter 110 to pass to the nonazide propellant charge 104 located
within a first combustion chamber 122. A first barrier wall 124 is
positioned to extend between the igniter tube 118 and a propellant
retainer sleeve 126 to form a second combustion chamber 128
positioned above the first chamber 122 within the housing 102.
Propellant charge 106 is located within the second combustion
chamber 128. A second barrier wall 129 is positioned to extend
between the igniter tube 118 and sleeve 126 to form a third
combustion chamber 130 above the second chamber 128 within housing
102. Propellant charge 108 is located within the third chamber 130.
The retainer sleeve 126 has a plurality of apertures 131 therein to
permit a radially outward passage of gas generated by the
propellant charges 104, 106 and 108. The filter 109 comprises a
fine wire mesh annulus that is resiliently axially compressed
between the housing portions 112 and 114 upon assembly thereof. The
filter 109 is radially retained by a relatively heavy wire screen
132 that accommodates radial expansion of the filter element 109
due to longitudinal compression upon assembly of the housing
components 112 and 114.
Just as with the first exemplary embodiment 10, the heat energy
generated by the combustion of the propellant charge 104 causes
subsequent delayed ignition of the propellant charges 106 and 108
by forced convection and/or conduction. The igniter flame front
only passes into the first combustion chamber 122, while the heat
produced therein conductively reaches the second and third
combustion chambers 128 and 130 via the plurality of apertures
131.
As described above, the present invention advantageously utilizes
the high combustion temperature of a nonazide propellant mixture to
allow the respective combustion chambers to be completely
segregated. In this manner, the overall inflation profile output by
the gas generator can be optimally controlled and tailored to
achieve a desired inflation profile. The conductively ignited
second and third propellant chambers of the present invention
achieves a desirable "low onset" S curve without sacrificing peak
inflation time or pressure. In addition, by adjusting the
respective sizes of the combustion chambers, utilizing more than
three chambers, and/or varying the propellant load in the
respective chambers, the inflation profile can be tailored to cover
a range of between approximately 10 to 90 percentile vehicle
occupants as opposed to conventional inflators which only provide a
nominal 50 percentile occupant inflation profile.
It will be understood that the foregoing description of the
preferred embodiment of the present invention is for illustrative
purposes only, and that the various structural and operational
features herein disclosed are susceptible to a number of
modifications, none of which departs from the spirit and scope of
the present invention as defined in the appended claims.
* * * * *